Control systems for friction clutch assemblies

ABSTRACT

Control systems for a friction clutch mechanism and a hybrid coolant pump. Friction clutch assemblies are positioned inside the motor housing and include softening springs which minimize parasitic clutch power consumption. The control systems use PWM to control the operation of solenoids which in turn operate the friction clutch assemblies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Patent Application No.61/474,895, which is related to U.S. Patent Application Ser. No.61/474,862 entitled Hybrid Coolant Pump (DKT 09105), U.S. PatentApplication Ser. No. 61/474,876 entitled Pulley Assemblies For VehicleAccessories (DKT 11001), U.S. Patent Application Ser. No. 61/474,928entitled Friction Clutch Assemblies (DKT 11002), and U.S. PatentApplication Ser. No. 61/474,907 entitled Compression Spring Members (DKT11003), all filed on Apr. 13, 2011.

TECHNICAL FIELD

A control system for a friction clutch mechanism and system isdisclosed.

BACKGROUND

Internal combustion engines for operation of vehicles such asautomobiles and trucks utilize a wide variety of accessory components.Many of the components, such as water pumps, have pulleys which aredriven by an accessory belt attached to the crankshaft of the engine andthus operate at some percentage of engine speed. Other components whichare pulley driven by an accessory belt include air conditionercompressors, generators, and the like.

Efforts are being made today to reduce the power consumption of engineaccessories in order to improve fuel economy and reduce emissions. Itwould be preferable if such accessories, such as water pumps, could bemade to operate at variable speeds or with less power in order to reducethe load on the engine and, in turn, improve fuel economy and reduceundesirable emissions from the engine.

SUMMARY OF THE INVENTION

A control system for vehicle components is disclosed. In a preferredembodiment, the control system is used to control the operation of afriction clutch assembly for a water pump. The water pump preferably hastwo modes of operation, a first mode mechanical driven by the enginebelt, and a second mode operated by an electric motor, such as abrushless DC (BLDC) motor.

The components for the two modes of operation in a preferred embodimentare contained within a housing that includes the pulley member as partof the housing. A shaft connected to the impeller of the water pump ispositioned in the housing and is controlled by one mode of operation orthe other, depending on certain factors.

The housing is turned at input speed by the belt of the enginepositioned on the pulley member. A friction clutch assembly is providedinside the housing to selectively allow operation of the water pumpmechanically by the pulley member. A solenoid is utilized to controloperation of the friction clutch.

The water pump is normally driven by the electric motor throughout mostof its range of operation. When peak cooling is needed, the mechanicalmode of operation takes over and the water pump is driven directly bythe pulley member. The friction clutch assembly includes a softeningspring member which minimizes the electrical power consumed by theclutch. The hybrid cooling pump has a variable speed control whichresults in the use of less power, the improvement of fuel economy, andthe reduction of emissions.

The friction clutch assembly has a compression spring member which isoperated by a solenoid. The force required to compress the spring memberlessens over displacement once a peak amount of force has been reached.The preferred control system operates the solenoid by pulse widthmodulation which provides current which is reduced when the solenoid isdisengaged.

Further objects, features and benefits of the invention are set forthbelow in the following description of the invention when viewed incombination with the drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a water pump in accordance with one embodiment of theinvention.

FIG. 2 is a cross-sectional view of the water pump shown in FIG. 1.

FIG. 3 is an exploded view of the components of the water pump as shownin FIGS. 1 and 2.

FIG. 4 illustrates a friction clutch embodiment which can be used inaccordance with the present invention.

FIG. 5 is an exploded view of the friction clutch as shown in FIG. 4.

FIG. 6 is an embodiment of a compression spring which can be used withthe present invention.

FIG. 7 is a side view of the compression spring member as shown in FIG.6.

FIG. 8 is an enlarged view of a portion of the compression spring memberin the uncompressed condition.

FIG. 9 is an enlarged view of a portion of the compression spring memberin the compressed condition.

FIG. 10 is a load-deflection curve of an embodiment of a compressionspring member for use with the present invention.

FIG. 11 illustrates an alternate embodiment of a compression springmember which can be used with the present invention.

FIG. 12 depicts another alternate embodiment of a compression springmember which can be used with the present invention.

FIG. 13 schematically illustrates the operating modes of a preferredembodiment of the present invention.

FIG. 14 schematically depicts another embodiment of a compression springmechanism which can be used with the present invention.

FIGS. 15 AND 16 illustrate a planar and side view, respectively, of oneof the buckling beam members utilized with the embodiment shown in FIG.14.

FIG. 17 schematically illustrates an electromagnetic clutch mechanism.

FIG. 18 schematically illustrates a solenoid control system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purpose of promoting and understanding the principles of thepresent invention, reference will now be made to the embodimentsillustrated in the drawings and specific language will be used todescribe them. It will nevertheless be understood that no limitation asto the scope of the invention is hereby intended. The invention includesany alternatives and other modifications in the illustrated devices anddescribed methods and further applications of the principles of theinvention which would normally occur to persons or ordinary skill in theart to which the invention relates.

The present inventions described herein particularly relate to improvedcontrol systems for hybrid coolant pumps which are used to circulate thecoolant in an engine, such as an automobile internal combustion engine.However, the present invention can also be used for other engineaccessory devices. Moreover, several other components, mechanisms andsystems described herein, including, but not limited to, the compressionspring members, the friction clutch assemblies, and the pulleyassemblies can have significant uses in other devices and systems.

As a coolant pump, the pump is electrically driven under mostconditions. However, it also can be mechanically engaged where morecooling is required. Thus, when the vehicle is being driven under mostnormal conditions, the water pump is being driven and operated by theelectric motor.

During “worst case” cooling conditions, such as when the vehicle isheavily loaded, when it is pulling a trailer, when it is going up hillin the summertime, etc., the water pump is adapted to be mechanicallydriven by the belt directly from the engine. This provides the necessarycooling under such circumstances.

In accordance with a preferred embodiment of the invention, the electricmotor is a brushless DC (BLDC) motor and the motor is positioned insidea pulley assembly. The pump is also adapted to be driven mechanicallywhen needed by the engine belt, such as a serpentine belt, attached tothe crankshaft of the engine.

The preferred embodiment of the present invention as described herein isparticularly adapted for use with trucks, passenger cars and off-highwayvehicles. Since the preferred embodiment also provides variable speedcontrol of the water pump, it uses less power from the engine and thusimproves fuel economy and reduces emissions.

A hybrid water pump embodiment in accordance with the present inventionis shown in FIG. 1 and referred to generally by the reference numeral20. The hybrid water pump includes a pulley assembly 22 and a water pumphousing 24. The pulley assembly 22 has a clutch housing member 26 and apulley member 28. The pulley member 28 has circumferential grooves 30for being driven by a belt (not shown).

A cross-sectional view of the water pump 20 is shown in FIG. 2 and anexploded view of the components of the water pump 20 is shown in FIG. 3.

The water pump has an impeller shaft 40 which is positioned within thepulley assembly 22 and also is attached to a water pump impeller 42. Theimpeller shaft 40 is held in place in the pump housing 24 by needlebearing 44 and middle bearing 84. A coolant seal 46 is used to preventcoolant in the pump from leaking into the pulley assembly.

A motor stator 50 is positioned inside a stator housing 52 in the pulleyassembly 22. A nut, such as a spanner nut 54, is used to hold the statorhousing 52 to the pump housing 24.

A second needle bearing 60 is positioned between the pulley member 28and the pump housing 24 in order to allow the pulley assembly 22 torotate freely relative to the pump housing.

A motor rotor 70 is positioned inside a front bearing carrier 72, whichpreferably is made from an aluminum material. The motor is preferably abrushless DC (BLDC) electric motor. A solenoid member 80 is positionedimmediately adjacent the front bearing carrier 72. A friction clutchassembly 90 is positioned adjacent the front cover of the motor housing22 and operated by the solenoid member 80. Bearing member 84 ispositioned between the bearing carrier 72 and the impeller shaft 40.

A fastening member such as a hex nut 92 secures the pulley assembly 22to the impeller shaft 40 via the front bearing 82. As indicatedparticularly in FIGS. 2 and 3, the pulley assembly 22 consists of twopieces, namely a pulley member 28 and clutch housing 26. Thisconfiguration provides for distribution of the belt load between therear needle bearing 60 and the front ball bearing 82, therebyeliminating overhung bearing loads. Consequently, the bearing loads areminimized resulting in a more durable and long-lasting product.

As indicated, the water pump is normally driven by the electric motor.The electric motor is electrically powered through a circuit board (notshown) connected to pin-type contact members 86. Electrical leads andwires can be insert molded in housing 25 and lead frame 29 in order tocarry the electrical signals to the electric motor stator 50 andsolenoid 80. The circuit board further communicates with the electroniccontrol unit (ECU) of the vehicle through the vehicle communicationnetwork such as a CAN network. The pump controller circuit board couldalso be positioned inside the pulley assembly 22 rearward of the statorhousing 52 and having a donut shape.

The speed of the motor and thus the water pump is selected according tothe cooling required for the engine. Sensors feed relevant data to theECU which then sends a signal to the pump controller requesting thedesired speed. The pump controller then determines whether the desiredspeed is best achieved using the electric motor or by engaging thefriction clutch and driving the impeller directly from the pulley.

FIG. 13 is a graph 200 schematically illustrating the functional modesof the hybrid pump. The speed of the engine is shown along the X-axisand the speed of the impeller is shown along the Y-axis in FIG. 13. Bothspeeds are shown in revolutions per minute (RPM).

The principal electric drive mode of the hybrid pump drive is shown at206. Peak torque is achieved by electric motor 208. Full pulley drive(a/k/a “belt drive”) is shown by line 210. Here the pump is being drivenmechanically by the engine through the accessory belt. The slope of line210 may be changed by modifying the pulley ratio between the enginecrank pulley and the pump pulley member 28.

An optional electrical drive area is shown at 212. This area representsthe region in which the electric motor is able to provide an“over-drive” feature where the pump can be spun at speeds greater thanthe mechanical input speed. The regions 214 and 216 are due to theefficiency loss in the electric drive mode from converting mechanicalenergy to electrical energy in the alternator and then back tomechanical energy in the electric motor. Although the pump could beoperated electrically in regions 214 and 216, it is more energyefficient for the pump to jump to the mechanical drive mode 210. In 202,the pump is OFF and the impeller is not rotating. In this embodiment,the pump is OFF regardless of the speed of the engine. It is alsopossible to drive the pump electrically when the engine is turned off.This is shown at 220.

An enlarged view of the friction clutch 90 is shown in FIG. 4, while anexploded view of the components of the friction clutch 90 is shown inFIG. 5. The friction clutch 90 includes a clutch carrier member 100, aflux plate member 102, a compression spring member 104, and a frictionlining carrier member 106. Pieces of friction lining material 108 areattached to its outer circumference of the carrier 106, as shown in FIG.4. The friction lining members 108 can be of any conventional frictionmaterial and can be of any size and shape. Although the friction liningmaterial is shown with a plurality of separate members, as shown inFIGS. 4 and 5, the friction lining can be a single piece or any numberof separate members positioned around the circumference of the frictionlining carrier member 106.

The friction lining material will wear over time as the hybrid pump isutilized. As this takes place, the capacity of the friction clutch 90will increase due to the design of the compression spring member 104which develops more force as the lining material wears.

An enlarged view of one embodiment of a compression spring member 104 isshown in FIG. 6. The spring member 104 is a “softening” spring membersince the force necessary to compress it decreases over time once itreaches a certain peak.

The spring member 104 has a plurality of holes or openings in order tobe attached to the friction lining carrier member and the clutch carriermember. In this regard, a series of four holes 110 are provided on thecompression spring member 104 in order to mate with openings 112 in thefriction lining carrier member 106. A plurality of rivets 114 or thelike are used to secure the compression spring member 104 to thefriction lining carrier member 106. The compression spring member can bejoined to the friction lining carrier member by any conventional method,such as by welding, brazing, threaded fasteners, etc.

The second series of openings in the compression spring member includefour openings 120. These openings mate with corresponding post members122 on the clutch carrier member 100. The post members 122 are deformedor swaged over when the friction clutch assembly 90 is assembled inorder to securely hold the components of the friction clutch assemblytogether.

When the friction clutch assembly 90 is in the engaged position, torqueis transferred from the pulley assembly 22 through the friction liningmembers 108 to the friction lining carrier 106. The friction liningcarrier then transfers torque through the compression spring member 104to the clutch carrier 100 which turns the impeller shaft.

The compression spring member embodiment 104 has an outer ring member130 and an inner ring member 132. The two ring members 130 and 132 areconnected together by a plurality of connecting members 134, 135, 136and 137. Enlarged portions of the compression spring member 90 are shownin FIGS. 8 and 9. When the spring member 104 is assembled in thefriction clutch assembly 90, the outer and inner ring members 130 and132, respectively, are held securely in place and are fixed so theycannot be moved radially toward or away from each other during operationof the friction clutch assembly.

In FIG. 8, the compression spring member is shown in the uncompressedposition. This is also shown in FIGS. 6 and 7.

When the spring member 90 is compressed to the position 142 shown inFIG. 10, the spring member forces the friction lining carrier member 106and friction lining members 108 against the conical friction surface 109(FIG. 2) inside of the clutch housing member 26 causing mechanicaloperation of the water pump. The clutch housing member 26 can bealuminum and the conical friction surface can be thermal spray coatedwith a variety of materials such as low carbon steel.

When the friction clutch assembly 90 is energized by the solenoid 80,the flux plate 102 is attracted to the solenoid assembly due to theforce developed in the air gap between the solenoid core 81 and the fluxplate. As the flux plate 102 moves toward the solenoid, the compressionspring member 104 is compressed separating the friction lining carriermember 106 and friction members from their engaged positions against theinside surface of the clutch housing member 26. In the compressedcondition, the connecting members 134, 135, 136 and 137 are buckled anddistorted such as in the manner schematically depicted in FIG. 9. Inthis position, the water pump is operated only by the electric motor.

The flux plate 102 is securely attached to the friction lining carrier106 through tabs 107 (FIG. 4). The attachment of the flux plate andfriction lining carrier may be through any conventional joiningtechnique such as spot welding, screws, rivets, or the like.

Axial travel of the clutch assembly is limited by the engagement of tabs103 on the flux plate 102 within pockets 101 on the clutch carriermember 100 (FIG. 5). This axial travel limit prevents the pole platefrom coming into contact with the solenoid core member 81 as the poleplate rotates with impeller speed and the solenoid core is stationary.

The load/deflection curve of the compression spring member 104 inaccordance with a preferred embodiment is shown in FIG. 10. As shown inFIG. 10, the load/deflection curve 140 reaches quickly to a maximumamount of force 140A and then needs less force in order to continue todeflect the spring member after it is starting to buckle and deform.This is shown by the second part of the curve 140B. This means that oncethe compression spring has reached point 140A, less force is needed tofurther deflect the spring and thus prevent the friction clutch assemblyfrom contacting the inside of the housing. In this regard, the clutchengaged position is shown at point 142, the working load of the springis indicated by line 144, the working length of the spring is shown byline 146, and the clutch disengaged position is shown at point 148.Thus, once the maximum amount of force necessary to buckle or deform thespring is reached, increasingly less force is necessary in order todeflect the spring further and thus allow complete operation of thewater pump by the electric motor. The softening spring member thusenables the parasitic electric power consumption of the clutchdisengagement solenoid 80 to be minimized. This is accomplished by pulsewidth modulating (“PWM”) the current supplied to the solenoid. Todisengage the solenoid the solenoid drive controller operates thesolenoid drive Field Effect Transistor (“FET”) at 100% PWM so fullcurrent is supplied to the solenoid. The controller has a currentsensing technology such that when the clutch seats in the fullydisengaged position it is able to sense the current change indicatingthe clutch is disengaged. At this point, the controller drops the PWM toa smaller level such as 10%, so less current is consumed by thesolenoid. Since the compression spring 104 develops much less force inthis position 148 as shown in FIG. 10 and the magnetic circuit is muchmore efficient as the air gap is smaller, the lower current level isstill adequate to keep the clutch in the disengaged position.

It is quite common in automotive accessories such as air conditioningcompressors, pumps, etc. to use spring engaged, electromagneticallydisengaged clutches to selectively turn on and off the drive to theaccessory component. This is typically done to conserve energy when thedevice is not needed. These devices are typically designed to be springengaged so the accessory device is powered in the event of a controlfailure such as a loss of electrical power. This is done to provide“Fail-Safe” functionality meaning that the device defaults to its “on”state when it is unpowered.

The primary disadvantage of these “Fail-Safe” clutch designs is thatthey require continuous electrical power to keep the device disengagedwhen it is not needed. For many accessory devices this condition canconstitute a large percentage of their operating life. Furthermore,these devices often require 20+ watts of electrical power, which can bea significant portion of the alternator output. On modern vehicles whichemploy a large number of electrical components (seat heaters, windowdefrosters, electric seats, and a host of other devices), it is notuncommon to exceed the maximum power capacity of the alternator.

A preferred embodiment of the present invention provides a means ofmitigating this problem by minimizing the parasitic power consumed byelectromagnetically disengaged clutches. Fundamentally this arrangementtakes advantage of the physical relationship between the force developedin the air gap of a magnetic circuit and the length of the air gap. Thisrelationship is described by the following Equation where m₁ and m₂ arethe respective field strengths of the two poles of the magnetic circuit,μ is the permeability of the free space and r is the distance betweenthe poles.

$F = \frac{\mu_{0}m_{1}m_{2}}{4\pi \; r^{2}}$

From the equation it is evident that the field strength falls off withthe square of the distance between the magnet poles. Furthermore, itevident from FIG. 17 that the spring force used to engage the clutchwill increase linearly when the solenoid is energized and the air gapcloses. This means that the solenoid will have excess capacity in itsclosed position since the magnetic field strength increases with thesquare of distance and the counteracting spring force only increaseslinearly with distance. Since the field strength of the magnetic polesare related to the current flowing through the coil and the number ofcoil turns, it is evident that less current is required to hold theclutch in the disengaged position than what is required to pull theclutch out of engagement. Furthermore, if the clutch engagement springis designed in such a way that the spring softens as it is compressed asdescribed herein, this effect will be even further pronounced.

To capitalize on this condition, the present invention employs a PWM(Pulse Width Modulation) control system for the solenoid as shown inFIG. 18. The PWM control system uses a PWM Driver (typically a FieldEffect Transistor and supporting circuitry) to pulse the solenoid poweron and off at a very high speed, typically on the order of a few hundredhertz. Since the solenoid provides a relatively large inductance whichprevents the current from changing instantaneously, this has the effectof reducing the average current delivered to the solenoid. The averagecurrent level can then be controlled by varying the duty cycle of thePWM Driver.

With this methodology, the PWM Driver is used to apply 100% duty cycleor full current to the solenoid to generate the maximum force in the airgap to pull the clutch out of engagement. Once the clutch is in thedisengaged position, the duty cycle can be reduced to a much lowerlevel, effectively reducing the average current supplied to the solenoidand consequently reducing the power consumption.

The PWM Driver can furthermore incorporate current sensing technology insuch a way that a microcontroller is able to monitor the currentsupplied to the solenoid. This is advantageous in that a current spikewill be evident on the solenoid supply line when the moving pole of thesolenoid seats against the travel limit. This current spike can be usedas a signal to the microprocessor that the clutch is in its retractedposition and the duty cycle can be reduced.

An alternate form of a compression spring 160 is shown in FIG. 11. Inthis embodiment, a series of connector members 162 are positionedbetween an outer ring 164 and an inner ring 166. When compression springmember 160 is used in a friction clutch assembly, the outer and innerring members 164 and 166 respectively, are constrained and fixed inplace. The inner connecting members 162 are comprised of radialcompression beams 163 and tangential flex arms 165. When the spring iscompressed, the tangential flex arms deform allowing the radial gaps 167to close as the spring flattens.

Another alternate embodiment of a compression spring member which can beused with the present invention is shown in FIG. 12. The spring member104′ is similar to spring member 104 described above, but does not haveouter or inner ring members. Instead, spring member 104′ has a pluralityof connecting members 134′, 135′, 136′ and 137′ which extend between theareas 105 of the openings 110′ and 120′. The latter openings 110′ and120′ are the same as, in the same locations as, and for the samefunctions and purposes as, openings 110 and 120 in FIGS. 4-6.

When the compression spring member 104′ is utilized in a friction clutchassembly, the connecting members 134′, 135′, 136′ and 137′ deform andbuckle similar to connecting members 134-137 described above providing asimilar “softening” spring member.

Another compression spring member (not shown) can be similar to thespring member 104 in FIG. 6, but only comprise an inner ring member oran outer spring member (i.e. not both), together with a plurality ofconnecting members.

Another “softening” compression spring mechanism is shown in FIG. 14,with one of its components being shown in FIGS. 15 and 16. Thismechanism 250 has a series of three “buckling beam” spring members 252,253, 254. The three beam spring members are also referred tocollectively by the reference numeral 258. As shown in FIG. 14, the beammembers 252-254 are indicated as being adapted to be attached to aninner ring member 260 and an outer ring member 262. When the beammembers are used in a friction clutch mechanism, such as friction clutchmember 90 described above, the ring members will be replaced by a clutchcarrier member and a friction lining carrier.

When the beam spring members 258 are attached to outer ring members orcarrier members, fastener members (not shown) will be positioned andsecured in the aligned openings 270 and 280. The fastener members can beany conventional type, but preferably are rivets. The openings can alsobe positioned over swagable post members in a manner as discussed above.

As shown in FIGS. 15 and 16, each of the beam spring members 252-254preferably are thin pieces of spring steel material having the shape andstructure shown. The beam spring members have a curved shape from a sideview, as shown in FIG. 16, with flat areas 272, 274, 276 where theattachment holes 273, 275, 277 are located.

The compression spring mechanism 250, or at least the group 258 ofbuckling beam spring members, can be used in the same manner and for thesame purposes as the compression spring members 104, 104′ and 164described above. The beam spring members 258 can buckle and deform underloads when the outer and inner ring members (or the clutch carriermember and friction lining carrier member) are forced toward each otherin operation of the water pump.

As indicated above, the present invention provides a “fail safe”friction clutch design. If the electrical system of the vehicle were tofail, the solenoid would be de-energized allowing the spring 104 toengage the friction clutch assembly to the clutch housing. Therefore thepump would operate in mechanical mode with the impeller driven by thepulley through the clutch assembly. The clutch is thus engaged whenevercirculation of coolant is needed.

Another design feature of the present invention is its modular assemblyconfiguration. It is common for coolant pump housings to vary widely inform and configuration from application to application. In order toaccommodate this wide variation of housing configurations with minimaldesign changes, the hybrid pump was designed so the water pump housing24 can be easily changed while the pulley assembly 22 and the componentscontained within it can remain largely unchanged.

Although the invention has been described with respect to preferredembodiments, it is to be also understood that it is not to be so limitedsince changes and modifications can be made therein which are within thefull scope of this invention as detailed by the following claims.

What is claimed is:
 1. A control system for a hybrid cooling pump, saidhybrid cooling pump comprising: a pump housing member; a pulley assemblyattached to said pump housing member; an impeller member positioned insaid pump housing for pumping coolant; an impeller shaft connected tosaid impeller member; an electric motor positioned inside said pulleyassembly and adapted to selectively rotate said impeller member; afriction clutch assembly positioned inside said pump housing member andadapted to selectively rotate said impeller shaft member; and whereinsaid pulley assembly and said electric motor operate separately torotate said impeller member; said control system comprising a solenoidfor activating said friction clutch assembly; and a drive controller forsaid solenoid, said controller disengaging said solenoid by operating at100% pulse width modulation to provide full current to the solenoid, andsaid controller significantly reducing the pulse width modulation whensaid solenoid is disengaged in order to consume less current.
 2. Thecontrol system as described in claim 1 wherein said friction clutchassembly comprises a compression spring member.
 3. The control system asdescribed in claim 2 wherein the amount of force necessary to compressthe spring member lessens over displacement once it has reached a peakamount of force.
 4. The control system as described in claim 3 whereinsaid compression spring member comprises a plurality of area membershaving openings therein and a plurality of deformable connecting membersextending between and connecting together at least two of said areamembers.
 5. The control system as described in claim 4 furthercomprising at least one ring member also connecting with a plurality ofsaid area members.
 6. The control system as described in claim 4 whereinan outer ring member and an inner ring member are provided, each of saidouter and inner ring members connecting with separate pluralities ofarea members.
 7. The control system as described in claim 2 wherein saidcompression spring member comprises a plurality of buckling beam springmembers.
 8. The control system as set forth in claim 1 wherein saidfriction clutch assembly comprises: a friction lining carrier member; atleast one friction lining member positioned on said friction liningcarrier member; a compression spring member fixedly attached to saidfriction lining carrier member; a clutch carrier member fixedly attachedto said compression spring member; and a flux plate positioned betweensaid clutch carrier member and said compression spring member andattached to said friction lining carrier member; wherein said flux plateactuated by said solenoid can cause said compression spring member tocompress.
 9. The control system as described in claim 8 wherein saidcompression spring member has an outer ring member, an inner ring memberand a plurality of deformable connecting members connecting togethersaid inner and outer ring members.
 10. The control system as describedin claim 9 wherein said friction lining carrier member is attached tosaid outer ring member, and wherein said clutch carrier member isattached to said inner ring member.
 11. The control system as describedin claim 10 wherein said plurality of connecting members deform whensaid friction lining carrier member and said clutch carrier member aremoved axially toward each other.
 12. The control system as described inclaim 8 wherein said compression spring member has a ring member and aplurality of deformable connecting members.
 13. The control system asdescribed in claim 8 wherein said compression spring member comprises aplurality of deformable connecting members.
 14. The control system asdescribed in claim 8 wherein the amount of force necessary to compressthe spring member lessens over displacement once a peak amount of forcehas been reached.
 15. The control system as described in claim 8 whereinsaid connecting members are positioned radially between said inner andouter ring members, and further comprising a plurality of tangentialflex arms and radial gaps, said radial gaps being positioned betweensaid flex arms and said outer and inner ring members.
 16. The controlsystem as described in claim 1 wherein said electric motor is abrushless electric motor.
 17. The control system as described in claim 8wherein said compression spring member comprises a plurality of bucklingbeam spring members.